This invention relates to bolt or stud tensioners of the type that include a housing to be set on a structure from which extends a bolt to be tensioned by a puller bar reciprocable in said housing while a nut on the bolt is tightened against said structure. More particularly, the invention is concerned with mechanism for connecting said puller bar to the bolt, which comprises a socket including a plurality of complemental segments having surfaces coactive with surfaces on the bolt and being mounted on said puller bar and movable into a first position into loosely surrounding relation to the bolt and into a second position wherein said surfaces on said segments interlock with said surfaces on said bolt, and mechanism for releasably locking said segments in said second position. U.S. Pat. Nos. 3,008,362, 3,128,990 and 3,844,533 are examples of such tensioners.
The prior art tensioners leave much to be desired in reliability and efficiency, and the mechanisms for manipulating and locking the socket segments require manual operation which consumes excessive amounts of time and labor.